Azacytidine (AZA) is the current standard of care for frontline patient treated with high-risk MDS and is clinically active in all type of MDS, however, 50% of the patients will never respond. Vorinostat is an orally available HDAC inhibitor with clinical activity in MDS and proven in vitro synergy with AZA. Patient treated upfront with a combination of this agents have shown more responses based on phase I/II data. In the present study, we will use the combination of these two drugs to try to create a synergetic effect and generate a response for patients who experienced treatment failure after AZA.